ANATOMY AND PHYSIOLOGY OF A SNAIL. 41 



this flagellum is given off from the base of the penis. The 

 penis sac during copulation is exserted ; attached to it is a 

 retractor muscle. The flagellum, with the posterior part of the 

 penis, secretes the spermatophore or capreolus. This is a body 

 formed of mucus with its edges folded inwards, so as to form a 

 groove in which spermatozoa becomes lodged, and more or less, 

 as it were, glued together into a mass. When the flagellum is 

 absent the spermatophore may be formed in the vas deferens 

 (Hyalinia) or in the penis (Anon). The flagellum is absent in the 

 American Helices. In Lo/igo vulgaris, and in many other forms, 

 a special pouch is developed in the yas deferens for the 

 spermatozoa ; this is known as Necdhains pouch. According to 

 the researches of Ash ford the flagellum of Testacella haliotidea 

 has a special retractor muscle. 



The oviduct, like the flagellum, gives off in its course a 

 diverticulum the spermatheca or receptaculum seminis the 

 function of which is to receive during coition a spermatophore 

 derived from another snail. This structure consists of a globular 

 head the Swammerdamian vesicle lying near the albumen 

 gland, and of a duct the duct of the spermatheca. In Helix 

 aspersa, and in other members of the genus to which it belongs, 

 there is an additional diverticulum given off which ends near the 

 aorta, and may possess a globular head. Below the point of 

 origin of the spermatheca the oviduct is generally spoken of as 

 the vagina; this runs forwards to open side by side with the 

 penis into a common genital cloaca or vestibule. In the genera, 

 Limncea, Planorbis, and Ancylus the male aperture (genial 

 aperture] is distinct from the female aperture (ps vagina), the 

 former being the more anterior of the two. The consequence 

 is that, anatomically, at any rate, self-fecundation is possible in 

 them, and this has been actually observed in Limncea auricularia. 

 Into the vagina open two structures, the mucous or finger- 

 shaped gland, and the dart-sac. The former of these consists of 

 a pair of tufted tubular glands, which secrete a highly refractile 

 fluid that is poured out when coition takes place. The dart-sac 

 is a p,'ar-shaped organ, containing in its interior a peculiar 

 spicule, known as the dart or spiculum amoris, which is of a 

 calcareous nature, except in Vitrina efangata, where it is chitinous. 



